VM100 Extension Tube Kit:
Extension Tube Kit allows a lens to be focused on object that is nearer to the camera than the normal lens focus movement provides. Extension Tube Kit is consists of 6 metal spacers and barrels of the following length (0.5, 1.0, 10.0, 20.0 and 40.0mm). By using these individually or in combination between the lens and camera, the lens can be focused at various distances.
Here is the specification for VM100 Extension Tube Kit.